Patent Application
20110242203
1. Field of the Invention
This invention relates to an inkjet printing apparatus including a plurality of inkjet heads.
2. Description of the Prior Art
Conventionally, in an inkjet printing apparatus including inkjet heads each having numerous inkjet nozzles, cleaning by suction (suction purge) is carried out for the inkjet heads in order to eliminate a printing failure called missing nozzle due to clogging of part of the inkjet nozzles.
The inkjet recording apparatus described in Japanese Unexamined Patent Publication No. 2008-213216, for example, includes caps for individually covering discharge opening groups (inkjet heads), a pump for drawing ink by suction from ink discharge openings (inkjet nozzles) into the caps, and switch valves respectively mounted on connecting paths connecting the individual caps to the pump. In this inkjet recording apparatus, by selectively opening the switch valves mounted on the connecting paths communicating with the respective caps of the discharge opening groups (inkjet heads), for example, only the cap covering an inkjet head which includes an inkjet nozzle failing to discharge ink can be connected to the pump, to undergo a suction purge for individually sucking the ink.
An inkjet printing apparatus has also been proposed, which includes a cleaning mechanism capable of a general suction which carries out suction for a plurality of inkjet heads collectively, and an individual suction for only one inkjet head (see International Publication No. 2007/058139). This cleaning mechanism is formed of a cap for individual suction, which is one of caps for individually covering a plurality of inkjet heads, and which may be connected to a pump through a tube, the other caps being connected to the pump through a tube branched to be connected to the plurality of caps, a first switch valve for switching sucking operation of the plurality of caps at the same time, and a second switch valve for switching sucking operation of only the cap for individual suction. When carrying out the general suction, all the plurality of inkjet heads are covered with the caps, and the first and second switch valves are opened. When carrying out the individual suction, only one inkjet head is covered with the cap for individual suction, the first switch valve is closed, and the second switch valve is opened, thereby allowing the desired inkjet head to undergo the suction.
However, with the apparatus described in Japanese Unexamined Patent Publication No. 2008-213216, it is necessary to arrange numerous electromagnetic switch valves corresponding to the number of caps, which poses a problem of enlarging the apparatus and increasing production cost. Driving the numerous electromagnetic switch valves also poses a problem of increasing power consumption, and thus increasing running cost.
On the other hand, the apparatus described in International Publication No. 2007/058139 carries out a cleaning operation for each inkjet unit having a plurality of inkjet heads juxtaposed in one direction. Therefore, when an individual suction of the inkjet heads is carried out, depending on the position in an inkjet unit of the inkjet head requiring suction, an extended time is consumed in moving the inkjet unit for positioning the inkjet head relative to the cap for individual suction. This poses a problem of taking a long time in cleaning the inkjet head.
The object of this invention, therefore, is to provide an inkjet printing apparatus having a simple construction, and yet capable of reducing ink consumption and cleaning inkjet heads promptly.
The above object is fulfilled, according to this invention, by an inkjet printing apparatus having a plurality of inkjet heads each with a plurality of inkjet nozzles, a plurality of caps respectively corresponding to the plurality of inkjet heads, a plurality of pipelines respectively connected to the plurality of caps, and a suction device for sucking ink from the plurality of inkjet nozzles through the plurality of caps and the plurality of pipelines, the apparatus comprising a connection switching device including a suckout port connected to the suction device; a switch element connected to and rotatably supported by a driving device, the switch element having a communication path formed therein to communicate with the suckout port; and a plurality of intake ports arranged equidistantly from a rotation center of the switch element, the plurality of pipelines being connectable to the intake ports; wherein the plurality of pipelines are selectively connected to the suction device by rotating the switch element to move the communication path to a position for communicating with one of the intake ports.
Such inkjet printing apparatus, with the connection switching device for selectively connecting the plurality of pipelines to the suction device, can reduce consumption of the ink due to a suction purge of the inkjet heads not requiring the suction purge. The apparatus can also carry out selectively quick cleaning of the plurality of inkjet heads.
In one preferred embodiment, the inkjet printing apparatus has a plurality of inkjet heads for a single ink color.
Other features and advantages of the invention will be apparent from the following detailed description of the embodiments of the invention.
For the purpose of illustrating the invention, there are shown in the drawings several forms which are presently preferred, it being understood, however, that the invention is not limited to the precise arrangement and instrumentalities shown.
An embodiment of this invention will be described hereinafter with reference to the drawings.
This inkjet printing apparatus is constructed to carry out printing by discharging inks from inkjet nozzles to a long recording medium M wound on a pair of winding rollers 43 and moving in one direction as driven by a drive motor 41. The apparatus includes a controller 20, an inkjet head group 10 and a cleaning section 30.
The controller 20, based on image information and others, performs printing controls such as driving the drive motor 41, monitoring an amount of movement of the recording medium M by an encoder 42 and adjustment of ink discharge from the inkjet nozzles. The controller 20 also controls operation of the cleaning section 30 for cleaning inkjet heads 110 (see
The inkjet head group 10 includes inkjet units 100 for respective ink colors of Y (yellow), M (magenta), C (cyan) and K (black) arranged in the direction of movement of the recording medium M. Each inkjet unit 100 has a plurality of inkjet heads 110, each with numerous inkjet nozzles, arranged in the direction of width of the recording medium M which is perpendicular to the direction of movement of the recording medium M. Thus, this inkjet printing apparatus performs what is called one-pass printing in which printing is completed with the recording medium M once passing under the inkjet head group 10, without reciprocating the inkjet heads 110 in directions perpendicular to the direction of movement of the recording medium M.
The cleaning section 30 includes a connection switching device 50 to be described hereinafter, suction caps 31a-31h (which may be collectively called “suction caps 31”) for covering, respectively, the eight inkjet heads 110a-110h juxtaposed on the inkjet unit 100, tubes 32a-32h (which may be collectively called “tubes 32”) connecting the respective suction caps 31a-31h to the connection switching device 50, a suction pump 34 acting as a suction device for applying suction to the respective suction caps 31a-31h, and an electromagnetic switch valve 33 mounted on pipeline 35 extending between the connection switching device 50 and suction pump 34. When cleaning the inkjet heads 110, the inkjet unit 100 moves from a printing position for executing printing to a cleaning position shown in
The connection switching device 50, as shown in
The switch element 60 has a circular shape with a suckout port 63 formed centrally thereof for discharging objects sucked into the connection switching device 50 out of the connection switching device 50, and with a communication path 62 formed inside to extend from the suckout port 63 to a peripheral position. The stepping motor 57 connected to the back of the switch element 60 through a shaft 58 rotates the switch element 60 to move the communication path 62 to a position for communicating with intake ports 61a-61l (which may be collectively called “intake ports 61”) of the cap support 54 to be described hereinafter. The suckout port 63 is connected to the pipeline 35 communicating with the electromagnetic switch valve 33 to be described hereinafter.
As shown in
A gap 66 is formed between the switch element 60 and cap support 54 to facilitate rotation of the switch element 60. An O-ring 64 is disposed as a seal member in the gap 66 between the communication path 62 and intake ports 61 in order that the communication path 62 of the switch element 60 communicates with the intake ports 61 of the cap support 54 without the gap. With rotation of the switch element 60 as driven by the stepping motor 57, this O-ring 64 moves through the gap 66 between the switch element 60 and cap support 54. In order to support this O-ring 64, a contact support member 65 is disposed in the communication path 62.
The contact support member 65 has a substantially cylindrical hollow shape, and contacts and supports the O-ring 64 in the gap 66 between the switch element 60 and cap support 54. The contact support member 65 has a surface for contacting the O-ring 64, and this contact surface has a taper such that its outer shape becomes larger toward the intake ports 61 of the cap support 54.
In a gap between concentric circular shapes like the gap 66 between the switch element 60 and cap support 54, in which the O-ring 64 contacts arcuate surfaces, a deformation force acts on the O-ring 64 whereby, as shown in
Next, an operation for cleaning the inkjet heads 110 will be described.
In the state shown in
When the inkjet unit 100 moves to the cleaning position shown in
When an individual suction for an inkjet head 110 is desired, as described above, suction may be executed after aligning the position of the intake port 61 connected to the suction cap 31 corresponding to the inkjet head 110 for which a suction purge is desired and the position of the communication path 62, by rotating the switch element 60.
With the flow path connections being selectively switchable as above, when a suction purge is desired for a plurality of inkjet heads 110, e.g. when a suction purge is desired for the inkjet heads 110b, 110f and 110h, the flow path connections may be switched by rotating the switch element 60 to place the communication path 62 in communication with the intake ports 61b, 61f and 61h in the stated order, and the electromagnetic switch valve 33 opened and closed repeatedly. Further, when a general suction is desired for the inkjet head 110, the flow path connections may be switched by rotating the switch element 60 to move the communication path 62 successively relative to the intake ports 61a-61h, for example, and the electromagnetic switch valve 33 opened and closed repeatedly as corresponding to the flow path connection switching. After a suction purge is carried out for all the inkjet heads 110a-110h, the stepping motor 57 may be operated to return the position of the communication path 62 to the origin to communicate with none of the intake ports 61a-61l.
In this embodiment, as described above, the flow paths for cleaning, individually connected to a plurality of inkjet heads 110, can be switched easily and quickly only by rotating the switch element 60. For both the individual suction and general suction, a cleaning operation can be carried out in a short time. A greater effect of shortening the cleaning time by individual suction can be secured with the inkjet recording apparatus which uses many inkjet heads 110 for each ink color, as where three or more inkjet heads 110 are arranged for a single ink color.
In the foregoing embodiment, the number of tubes connectable to the connection switching device 50 is 12. However, this invention is not limited to this number, as long as it is more than the number of inkjet heads 110 arranged on one inkjet unit 100, for example. Further, although the switch element 60 of the connection switching device 50 employed in the foregoing embodiment is shaped circular, its shape can be polygonal instead.
The foregoing embodiment has been described with relation to an operation for cleaning the inkjet heads 110 having inkjet nozzles for discharging ink. The connection switching device 50 described hereinbefore is applicable also to cleaning of a plurality of inkjet heads having nozzles for discharging various solvents other than ink, such as a coating agent.
This invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.
This application claims priority benefit under 35 U.S.C. Section 119 of Japanese Patent Application No. 2010-78488 filed in the Japanese Patent Office on Mar. 30, 2010, the entire disclosure of which is incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-78488 | Mar 2010 | JP | national |
